COSMIC RAY EXPOSURE DATING APPLIED TO RELICT ROCK GLACIERS IN THE CANTABRIAN MOUNTAINS (NORTH IBERIAN PENINSULA; NORTH ATLANTIC REGION)

• Main Authors: Rodríguez-Rodríguez, Laura, Jiménez-Sánchez, Montserrat, José Domínguez- Cuesta, María, Rinterknecht, Vincent, Pallàs, Raimon, Aumaître, Georges, Bourles, Didier, Keddadouche, Karim
• Other Authors: Universidad de Oviedo Oviedo, Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2017
• Subjects: relict rock glaciers; surface exposure dating; last deglaciation; Cantabrian Mountains; North Atlantic region; [SDE]Environmental Sciences; Cronus; Oliva; North Atlantic
• Online Access: https://hal.science/hal-03546763

International audience Last deglaciation was characterized by remarkable recession of the glacier fronts and a progressive migration of the periglacial belt towards the highest areas of the Cantabrian Mountains. Block fields, block streams, rock glaciers, protalus ramparts, patterned grounds and debris slopes developed, reaching altitudes down to 1400–1300 m asl (Gómez-Villar et al., 2011; Oliva et al., 2016). Particularly, rock glaciers show an outstanding preservation state close to the back wall area of the north-facingglacial cirques, specially on quartzite sandstone, but there is still a lack of direct chronological constrain of their activity (García-Ruíz et al., 2016; Oliva et al., 2016). Thus, the debate on whether their latest activity was mostly during the Younger Dryas (GS-1, 12.9–11.7 ka) or spanned the entire deglaciation is still open. We present a dataset of Be-10 Cosmic Ray Exposure (CRE) ages for two rock glaciers sampled at the headwall areas of the Monasterio and Porma valleys in the Central Cantabrian Mountains. Surficial samples were collected from ten boulders of the foremost frontal ridge of both relictrock glaciers. Sample treatment and Be-10 extraction were performed at Laboratori de Cosmonúclids Terrestres (University of Barcelona, Spain), while the isotopic ratio Be-10/Be-9 of each sample was measured at the French 5 MV AMS facility ASTER (Aix-en-Provence, France). CRE ages were computed via the online exposure age calculator formerly known as the CRONUS-Earth exposure age calculator, using version 2.3 (Balco et al., 2008). Results suggest that rock glaciers remained fully active until 13 ka in favorable northeast-facing glacier cirque settings of the Central Cantabrian Mountains,although movement cessation could have been reached earlier (ca. 15.7 ka) in less favorable settings.